Motexafin gadolinium reacts with ascorbate to produce reactive oxygen species

Motexafin gadolinium (MGd) oxidizes ascorbate, in neutral buffer and in cell culture, forming reactive oxygen species and a coordination polymer with oxalate.     

The Surface Energy of MgO: Multiscale Reconstruction from Thermal Groove Geometry

The surface energy of MgO is determined using experimental data collected from equilibrated thermal grooves circumscribing island grains. Local equilibrium assumptions at each groove require that the Herring equations be satisfied at each data site, thereby yielding a large and overdetermined system of equations involving the surface energy . This inverse problem is then solved using a new technique that is statistical in nature and multiscale in implementation. The resulting discrete solution represents a statistically significant representation of the surface energy of MgO as a function of surface orientation. Comparisons to results derived from a more traditional approach, along with suggested further applications, are discussed.     

Heteronuclear decoupling interference during symmetry-based homonuclear recoupling in solid-state NMR

We examine the influence of continuous-wave heteronuclear decoupling on symmetry-based double-quantum homonuclear dipolar recoupling, using experimental measurements, numerical simulations, and average Hamiltonian theory. There are two distinct regimes in which the heteronuclear interference effects are minimized. The first regime utilizes a moderate homonuclear recoupling field and a strong heteronuclear decoupling field; the second regime utilizes a strong homonuclear recoupling field and a weak or absent heteronuclear decoupling field. The second regime is experimentally accessible at moderate or high magic-angle-spinning frequencies and is particularly relevant for many realistic applications of solid-state NMR recoupling experiments to organic or biological materials.     

Observed effects of a changing step-edge density on thin-film growth dynamics

We grew SrTiO(3) on SrTiO(3)(001) by pulsed laser deposition, while observing x-ray diffraction at the (00(1/2)) position. The drop DeltaI in the x-ray intensity following a laser pulse contains information about plume-surface interactions. Kinematic theory predicts DeltaI/I = -4sigma(1 - sigma), so that DeltaI /I depends only on the amount of deposited material sigma. In contrast, we observed experimentally that |DeltaI /I| < 4sigma(1 - sigma) and that DeltaI /I depends on the phase of x-ray growth oscillations. The combined results suggest a fast smoothing mechanism that depends on surface step-edge density.     

Mode-locked fiber laser frequency-controlled with an intracavity electro-optic modulator

We demonstrate a mode-locked, erbium-doped fiber laser with its repetition frequency synchronized to a second fiber laser via an intracavity electro-optic modulator (EOM). With servo control from the EOM (bandwidth approximately 230 kHz) and a slower speed intracavity piezoelectric transducer (resonance at approximately 20 kHz), we demonstrate stabilization of the repetition frequency with an in-loop rms timing jitter of 10 fs, integrated over a bandwidth from 1 Hz to 100 kHz. This represents what is to our knowledge the first time an EOM has been introduced inside a mode-locked laser cavity for fast servo action and the lowest timing jitter reported for a mode-locked fiber laser.     

Synthesis of a cyclic peptide containing norlanthionine: effect of the thioether bridge on peptide conformation

Two diastereomeric analogues of ring C of nisin incorporating a novel norlanthionine residue have been synthesized via a triply orthogonal protecting group strategy. A full structural study was carried out by NMR, which elucidated the conformational properties of the two peptides and enabled the identity of each diastereoisomer to be proposed.     

Redox modulation of benzene triimides and diimides via noncovalent interactions

[reaction: see text] Mellitic triimides undergo three sequential one-electron reduction processes whose potentials are significantly lowered in the presence of alkyl thioureas. The two sequential reductions of benzene diimides are similarly stabilized. Calculation of the relative free energy change between the different electronic states of the imide acceptors and their corresponding alkyl thiourea complexes indicates dramatic increases in hydrogen bond strength with increasing acceptor charge density.     

Dynamic and redundant regulation of LRRK2 and LRRK1 expression

Background  

Mutations within the leucine-rich repeat kinase 2 (LRRK2) gene account for a significant proportion of autosomal-dominant and some late-onset sporadic Parkinson's disease. Elucidation of LRRK2 protein function in health and disease provides an opportunity for deciphering molecular pathways important in neurodegeneration. In mammals, LRRK1 and LRRK2 protein comprise a unique family encoding a GTPase domain that controls intrinsic kinase activity. The expression profiles of the murine LRRK proteins have not been fully described and insufficiently characterized antibodies have produced conflicting results in the literature.